Russian forces are "stepping back on the battlefield" for the first time since 2022, the agency's head, Anne Keast-Butler, said in a speech, according to the British newspaper The Guardian.
New intelligence shows that almost half a million Russian soldiers have now been killed since the conflict began, she said.
The figure is higher than a current estimate by the Russian independent news sites Mediazona and Meduza, which put Russian deaths at around 352,000.
U.S. Senator Marco Rubio recently said that 15,000–20,000 Russian soldiers are killed every month.
